1. Field of Invention
The present invention relates to an apparatus for reducing transmission shock in an automatic transmission. More particularly, it relates to a transmission shock-reducing apparatus for an automatic transmission which serves to reduce transmission shock by securing robustness against impact torque produced in the course of the interconnections of clutches during a gearshift.
2. Description of Related Art
An automatic transmission, which is an apparatus for automatically shifting gear shift stages of a multi-stage transmission into an appropriate gear shift stage in response to a vehicle speed, generally includes at least one or more planetary gear set having sun gears, ring gears, and planet carrier as operating members to realize an automatic shift, and further includes a plurality of frictional engaging elements such as clutches and brakes to control the operation of the operating members.
The automatic transmission is provided therein with a hydraulic control system to hydraulically control such frictional elements, and serves to realize each of the shift stages so that the clutches and brakes selected in accordance with each of the shift stages may be controlled to be clutched or released.
The clutches among the frictional engaging elements serve to transfer power of an engine to the operating members of the planetary gear set, or to connect and disconnect the power transfer between the operating members.
Such clutches are formed with a plurality of clutch disks and frictional materials alternately inserted between a clutch hub and a clutch drum and serve to connect or disconnect the power transfer by applying a hydraulic pressure to a piston.
For example, when oil flows into a space between the piston and clutch drum through oil holes formed in the clutch hub during a gear shift, the piston enables the frictional material and the clutch disk to become in contact with each other by a hydraulic pressure, thereby the clutches are operated.
However, since such a conventional automatic transmission has difficulty eliminating basically backlash existing in a driving system and transient torque generated during shifting, a high hydraulic pressure is abruptly applied to the piston when the automatic transmission is operated and an abrupt impact in the automatic transmission may accordingly be generated, thereby resulting in transmission shock, clunk noise and the like, which are difficult to solve.
It has been well known that most of the problems generated in such a conventional automatic transmission are caused by such transmission shock occurred at the time of a link between the clutches (or a close contact of a clutch disk with a frictional material). The impact torque generated at that time is amplified due to backlash of a driving system and then transferred to a driver through a transferring system.
To reduce transmission shock of the conventional automatic transmission, a method of increasing a shift time (or transmission time) has been adopted. It, however, results in a shift response delay.
That is to say, transmission shock deteriorates when the shift time of an automatic transmission is reduced and the shift response (or transmission response) is delayed when the shift time is prolonged
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.